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Cassini makes 100th Titan flyby

Jenny Winder, News Writer
Mar 7, 2014, 8:00 UTC

Sen—NASA's Cassini spacecraft has conducted its 100th flyby of Titan, swooping down within 933 miles (1,500 kilometres) of Saturn's largest moon.

The large moon shares many Earth like characteristics including a thick atmosphere and surface liquids in the form of seas and rivers. It also rains on Titan. The surface liquid and rain are hydrocarbons such as methane and ethane. 

Each flyby gives us a little more knowledge of Titan and its striking similarities to our world. Even with its cold surface temperatures of minus 290 degrees Fahrenheit (94 kelvins), Titan is like early Earth in a deep freeze.

Since arriving at Saturn in 2004, Cassini's radar instrument has identified remarkable surface features on Titan. The features include lakes and seas made of liquid methane and ethane, which are larger than North America's Great Lakes, and an extensive layer of liquid water deep beneath the surface. Organic molecules abound in Titan's atmosphere, formed from the breakup of methane by solar radiation.

During this flyby the Radio Science Subsystem instrument (RSS) team will carry out a Titan Gravity science observation, one of only three in the entire Solstice Mission. The largest instrument on the mission, RSS is split in two parts: one on the spacecraft, the other at each of the three Deep Space Network complexes.

The RSS instrument's split personality allows it to measure the forces acting on the spacecraft by detecting slight changes in the frequency of radio signals sent from the spacecraft to Earth.

Recently it was discovered that radar could be used to determine the depth of a Titan sea. "It's something we didn't think we could do before," said Michael Malaska, an affiliate of the Cassini radar team at NASA's Jet Propulsion Laboratory. "The radar can measure the depth by receiving two different bounces: one from the surface and one from the bottom of the sea. This technique was used to determine that Ligeia Mare, the second largest sea on Titan, is about 160 meters (525 feet) deep. When coupled with some laboratory experiments, it gives us information about the composition of the liquid in Ligeia Mare, too."

As spring turns to summer in Titan's northern hemisphere for the first time since Cassini arrived at Saturn, scientists are looking forward to an exciting time for Titan weather, with waves and winds picking up. With increasing sunlight, the north polar lakes and seas can now be seen in near-infrared images, enabling scientists to learn more about their composition and giving them clues about the surrounding terrain.

"Methane is not only in the atmosphere, but probably in the crust," said Jonathan Lunine, a scientist on the Cassini mission at Cornell University, in a statement. "It's a hint there are organics not only in Titan's air and on the surface, but even in the deep interior, where liquid water exists as well. Organics are the building blocks of life, and if they are in contact with liquid water, there could be a chance of finding some form of life."